


How to Train Your Boyfriend

by Daniverse



Category: Fire Emblem Series, Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Demons, First Time, M/M, Plot What Plot/Porn Without Plot
Language: English
Status: Completed
Published: 2019-11-17
Updated: 2019-11-17
Packaged: 2021-02-08 04:24:15
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,844
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21470026
Author URL: https://archiveofourown.org/users/Daniverse/pseuds/Daniverse
Summary: "Just … what are you, anyway?"Sylvain's grin went devious as he gave the other man a wink and blew him a kiss."Just your friendly, neighborhood sex demon. Now sit back and let me give you a little demonstration."---Felix and Dimitri want to have a good first time, Annette suggests trying to communicate with a ghost to figure out the best way to do it. They accidentally summon Sylvain, who decides to helpfully show them the ropes.
Relationships: Dimitri Alexandre Blaiddyd/Felix Hugo Fraldarius, Dimitri Alexandre Blaiddyd/Felix Hugo Fraldarius/Sylvain Jose Gautier, Dimitri Alexandre Blaiddyd/Sylvain Jose Gautier, Sylvain Jose Gautier/Felix Hugo Fraldarius
Comments: 15
Kudos: 181





	How to Train Your Boyfriend

This was a stupid idea.

Dimitri and Felix were sitting together in their dorm room, lights shut off except for a few electronic candles - stupid campus rules not allowing real candles - encircling the two. Felix had confided in Annette that he wanted to finally have sex with Dimitri, and she had decided that the best way to do this was to "ask a ghost".

"Ghosts have had sex!" She asserted loudly, looking very confident as she said the most ridiculous thing Felix had ever heard. "Ghosts have totally had sex! They're gonna know what to do." Dimitri, for some reason, also thought this was a good enough idea to warrant trying, so now they were sitting across from each other, holding each other's hands over a Ouija board.

Felix took a deep breath as he read off the script Annette had prepared for them. "Oh spirits," he started, trying to keep the mockery out of his tone. "Please use this board and planchette to speak with us. If you are here, please show us."

The planchette rattled. Felix officially did not think this was a stupid idea anymore, and instead was properly fucking terrified.

Dimitri spoke next, which Felix was endlessly thankful for since he was pretty sure he had just swallowed his tongue. "Spirits, we are looking for someone to help us with love. We need your wisdom and guidance." The planchette rattled again and Felix wanted to die. It moved on its own, sliding first to the "S", then stopping. Felix broke his hold on Dimitri's hands and uncorked the bottle of rose oil that Annette had given them, coating finger in it before touching the planchette. It was ice cold to the touch.

It slid to the "Y", Felix lurching as it moved of its own volition. Dimitri seemed rightly spooked as well, dunking a finger in the rose oil and placing a hand on the planchette. It zipped around the board, finishing as it spelled "Sylvain". Felix looked up at Dimitri, confusion plain on his face.

"Do you have any idea what the hell a 'Sylvain' is?"

Dimitri shook his head. "Annette didn't tell you?"

"No. She didn't care to share what happens once it stops. Sounds like gibberish to me." They both pulled their hands away and stared at the board. The planchette began rattling wildly before it snapped clean in half. Felix's eyes went wide, his mouth falling open.

"She's gonna kill me." A thin plume of smoke spilled from the split planchette as the two men watched with terrified expressions on their faces.

All at once, the candles shut off. Dimitri yelped and Felix squeezed his eyes shut. _This wasn't happening_, he kept telling himself. Dimitri pushed the board away and hugged Felix close, burying his face in his hair.

The candles all turned back on, blinking on one by one. Sitting two feet across from them was a red haired man with beautifully freckled skin, wearing nothing but a pair of tight shorts. Resting atop his head were two large, curling horns and a little tail curled lazily on his knee.

"Can I help you?"

Felix yelled, holding Dimitri tight. Dimitri looked at the new figure, trying to put on a brave face. "Would you happen to be … Sylvain?" He grinned and waved at the two.

"Don't wear it out. Now then, I assume you two called me up?" Felix tried to calm down, but was still trying to do the math on how they summoned a person out of thin air.

"Er, yes. We were the ones who … who called you." Dimitri spoke up again, petting Felix's hair. "We want to have a good first time together. But, ah … we're not familiar with the methods of how to do so." Sylvain slapped both of his hands to his face in surprise.

"A newbie? _Two_ newbies? Oh, this must be my lucky day." He pointed at them both, Felix finally gathering the courage to let go of Dimitri and face this monster. "All right, who is fucking who." Felix pointed at Dimitri, his face beet red.

"H-he is. Fucking me, I mean." Dimitri's face was hidden behind his hands and Sylvain cooed at them both, reaching over to pat Dimitri's shoulder. He could feel his touch, which surprised him. He had assumed he would be incorporeal. His hand was large and warm, and Dimitri felt a little of his own tension releasing.

"Grats! How long you two been together?"

"Three years."

"Holy shit." Sylvain looked at Felix and eyed him up hungrily. "All right, I'll show you how it's done." Both hands wrapped around Felix's arms and lifted him, Felix yelping and throwing a kick. It connected and Sylvain winced, wrangling him into his lap.

"Hey, hey! Easy there, babe." Sylvain's fingers glowed purple and Felix stopped wriggling, biting hard into his lip as his face went hot.

"What was that?" Dimitri blinked at his boyfriend, sitting on this devil's lap, suddenly looking like he was _starving_. He had seen that look on him a few times; when his hand was wrapped around Felix's cock and stroked him fast and sloppy.

"Just gave him a little of the juice. It'll make this much easier for you to watch." He pulled his hand away, wiggling each of his fingers for Dimitri as purple sparks crackled off them.

"Just … what are you, anyway?"

Sylvain's grin went devious as he gave the other man a wink and blew him a kiss.

"Just your friendly neighborhood sex demon. Now sit back and let me give you a little demonstration." He nestled his head into the crook of Felix's neck and pressed kisses along it, Felix's neck tipping back as he let out a soft gasp each time.

"You guys have lube?" Dimitri nodded quickly and got up, going over to his bedside table and tossing the bottle to him. Sylvain caught it, popping the cap open with a thumb. "Follow up question." He slid Felix's pants and boxer briefs to around his knees, Felix wriggling at the close contact. He was already half hard, and he hadn't even been touched yet. Dimitri had to tell himself to breathe otherwise he was sure he'd forget.

"Have you fingered him before?"

"I've fingered myself. Dimitri's done it once." Felix spoke up with his usual bite in his voice, despite still sitting compliant in the Incubus' lap.

"Mm, good. We're not starting from square one." He hummed in Felix's ear and gave a it a playful bite, Felix blushing down to his neck. Sylvain had pushed Felix's shirt up enough that his stomach was exposed, a second hand rubbing circles on his hip. "Then we can move right along with this." He shifted Felix in his lap so that he was leaning on one side, cheek pressed against one of Sylvain's broad shoulders. Sylvain's hand was now palming Felix's ass, squeezing hard and gave him a small, playful slap.

Dimitri found himself rooted to his spot, eyeing the little purple sparks that jumped from Sylvain's hand to Felix's body. His whole body had shivered from the spank and he _moaned_, and now Dimitri wished he could do anything even close to that himself. The idea of raising a hand to Felix made his knees wobble. He snapped out of his thoughts as Sylvain pointed to the open bottle of lube and gestured to him.

"Wanna do me a solid? A little tough to do this one handed." Dimitri leaned over and poured some of the lube onto Sylvain's fingers, gently placing it back down next to him. He scooched himself closer on the carpet, palming himself through his pants. "Okay, since you aren't super familiar with this, pay attention." He angled Felix so that Dimitri could see his ass, pulling him apart slightly with his unslicked fingers.

"The actual finger isn't the part that feels good. He'll feel best along the rim, and then against the prostate." His pointer finger dragged lazily along Felix's rim as he spoke, Felix's breath catching as he let out a few shaky moans. "Do me another favor Blondie and let me see what he's working up to." Dimitri nodded and fumbled with his belt, hastily unzipping his pants to pull out his own cock. Sylvain's eyes trailed down and he let out a low whistle.

"Oof. That's a lot, newbie." Sylvain let go and gave him another slap, harder this time. Felix cried out and looked back at him, his expression a mix of lustful and furious.

"Why do you think we were desperate enough to do this?"

Sylvain laughed, squeezing Felix's glowing behind and returning his finger to massage at his entrance. "I get it, okay." And with that, he slipped the first finger in all the way to his last knuckle, feeling Felix clamp down tight around him.

"He fingered himself already."

"F-fuck you. I wanted to be prepared."

Sylvain laughed again, soft and sweet, as he nuzzled against Felix's cheek. "Such a considerate boyfriend." Sylvain's finger curled, grazing Felix's prostate and he rutted back, hand flying down to stroke himself through the pleasure. "Hey, hey, chill out." Sylvain gently batted Felix's hand away and he whined, biting into his lip. "You gotta last so I can show Blondie McHugeCock over here how to make you feel good and not split you down the middle." He teased a second finger and slid it in half way, scissoring to stretch Felix out. He gasped and held onto Sylvain for dear life.

"You can just call me Dimitri, you know. And my boyfriend is Felix." Dimitri was stroking himself slow and steady, eyes trained on Felix's hole filled with the fingers of a complete stranger. He tried not to think about how hot it was to see Felix from this angle, breathing hard and fast while this demon was stretching him open.

"Fine, fine. Did either of you have a position in mind? I can do it like this, but it's easier to see if I just nail him doggy style."

Dimitri's mind went blank, trying to remember what sexual positions even existed. There was a long pause before Felix blurted out "I don't care, just do it already!" And Sylvain popped both of his fingers out with a wet noise, leaving Felix groaning at the loss of feeling.

"Doggy style it is, then. Come on, up." Felix got up slowly, carefully, his cock straining hard against his stomach and sticky with precome. Dimitri leaned in to kiss him, Felix grabbing the back of his head and kissing him hard. He pushed his tongue in and dominated his boyfriend's mouth, leaving Dimitri breathless and panting as he pulled back.

"You're welcome."

Dimitri just nodded dumbly, falling back on his hands as Felix got on all fours, his hair having long since lost its tie and hanging down his face. He looked beautiful; sweat on his brow, cheeks flushed, pupils blown wide as he presented himself to Sylvain. Sylvain had slipped off the only article of clothing he had, stroking an equally large member to coat it in lube.

"Fair warning, it's gonna be cold. Just comes with the territory, sorry sweetheart." He pressed his head up against Felix and he gasped sharply.

"It's like a fucking icicle, what the hell is wrong with you?"

"Blah blah demon things blah blah blah. Who cares, you'll forget about it in like five seconds." He was flapping his hand dismissively as he spoke, his other hand gripping Felix's hip as he started to push himself in.

"Go easy, it's gonna hurt the first time around. Try to counterbalance that as much as possible with movement and hitting the prostate. And of course you can also work him under you too, it'll tighten him up real nice." Sylvain's second hand went to the base of his cock, guiding him slowly into Felix. Felix's elbows shook as he let out a low, uncomfortable sounding noise.

"Are you okay?" Dimitri broke his hard gaze on Felix's plump behind getting penetrated to look at his boyfriend with concern on his face.

"I-it's fine, just a lot."

"And he is much bigger than me." Sylvain reminded him. Felix groaned and let himself fall forward onto his forearms, glaring angrily at Dimitri's massive dick.

"You two love birds are distracting me! Come on, Dimitri, get back over here." Dimitri pressed a kiss to Felix's forehead and offered him a gentle smile.

"I love you. You look beautiful." With that, he moved back to Sylvain and absently rubbed at Felix's lower back.

"Start slow and shallow to get him used to the feeling. Once he gives you the okay, then you can start getting a little wild." He gave a wink and pulled back about halfway before slamming back in, Felix letting out a strangled noise. He started to pick up a steady pace, pumping himself with a practiced rhythm, the sound of skin slapping against skin filling the room. Dimitri's mouth was dry as he rubbed his hand over the head of his cock, biting back a moan of his own as he watched Felix urge himself to meet back at every thrust, crying out each time.

Sylvain reached a hand underneath Felix and pressed his chest up against his back, squeezing him tight. "Come on, baby. You know you wanna come for him. Look how bad he wants it." Felix looked back and Dimitri had hiked up his own shirt, stroking himself fast and unable to pull his eyes away. Sylvain started slamming in hard, hitting his prostate each time as Felix screamed and saw white, coming onto his chest. Sylvain pulled out and grinned, still hard and dripping as Felix collapsed onto the ground and rolled onto his side.

"... Holy shit." Felix was breathing hard, looking like he had just found God and it had been buried deep inside his ass the entire time. Dimitri refused to let himself finish yet, he had to feel Felix himself. He couldn't just leave it all to Sylvain. Before he could go cuddle his blissed out boyfriend, Sylvain started snapping his fingers insistently to attract his attention.

"Hey. Hey, we're not done yet."

"We're … not?"

Sylvain sighed and pointed at Dimitri's cock. "No way, you've got a practice exam." Sylvain turned himself around and spread both his cheeks, Dimitri's eyes falling on the gift presented to him. "He's gonna be too overstimulated anyway. Come on, beautiful. Give me a little taste." His grin was wide and knowing, so tempting as Dimitri made his way over.

"So first … fingers." Dimitri muttered to himself. Sylvain rolled his eyes and knocked at the bottle of lube with the back of his foot.

"Chop chop. After plowing your man's ass I want to see what he's getting into." Dimitri tried to ignore him and slicked up two fingers, pressing the pad of his finger against Sylvain's entrance. He gave a hum of approval, Dimitri taking it as an okay to ease the rest of his finger in. He moved in slowly and curled, Sylvain biting his tongue as he let out a filthy moan.

"Mm … God, Felix, he even has thick _fingers_. You are going to be so whipped for this monster cock, I can already tell." Dimitri started thrusting his finger in, placing a hand on Sylvain's shoulder to get a better angle. Felix blushed furiously at him, throwing a glare up at Sylvain and flipping him off. Sylvain looked as if he had been about to quip back, but Dimitri teased a second finger and Sylvain's entire body shuddered instead.

Sylvain's tail dragged along Dimitri's forgotten member and he gasped, the tail feeling foreign to him. "Tell me how you wanna take him."

"Against the wall."

Sylvain nodded and let out another noise as the second finger entered him, spreading him out wide. "Give me one more finger for good luck and we'll reposition." The tail was now wrapped around his cock and was stroking him slow and idly, Dimitri resting a head against Sylvain's back as he let out sharp breaths. He pushed in the third finger and started finger fucking him hard, Sylvain rutting back against him.

"Such a quick learner, _fuck_." He sucked his lip in and let his eyes roll back, losing himself in the sensation. Dimitri pulled out quickly, Sylvain whimpering behind him. "How cruel. I bet you could make little Felix cum dry like that." Felix, feeling forgotten and now sufficiently scandalized, shook his head and covered his face.

"Just get this over with so he can leave."

"Gladly." Dimitri turned back at him and smiled. "I'll leave him a mess so you'll know exactly what you're getting into, my love." Felix gasped and watched, Sylvain pressing his body up against the dorm wall and leaning back, presenting his ass again and giving it a wiggle.

"Don't make promises you can't keep." Dimitri had gotten up as well, coating his hand in lube and giving himself a few perfunctory strokes. He took both of Sylvain's hips and positioned himself carefully, head pressing against Sylvain.

"You'll have to lift him up to do this, he's probably too short."

"Fuck you." Felix found he was half hard again, still a little sensitive as he pressed his thumb along the vein running along the underside of his cock while he watched.

Dimitri fisted a hand tight in Sylvain's hair, pale white skin contrasting against the crimson red locks and charcoal ram's horns, as he yanked his head back. Sylvain's smile was downright monstrous, his neck arched back as his Adam's apple jumped across his throat.

"I should've guessed he liked it rough."

"That's _enough_." Dimitri growled as he entered Sylvain, wasting no time as he buried himself to the hilt. He paused, letting his mind recalibrate as he got used to being surrounded by the immense tightness and heat of Sylvain's ass. He took a deep breath as he pulled himself almost completely out, only the head left within him. Sylvain tried to rut back against him, but found Dimitri's grip was tight around his hip, locking him in place.

"I am either the best sex teacher on the planet, or your boyfriend's a liar."

Felix rose a brow and looked at Dimitri curiously. "He's joking, right?"

"Felix, please tell me who you think I could do this to." He slammed back in hard, Sylvain crying out and shuddering against the wall.

"Good point. Continue." He fisted his cock and leaned back, Dimitri fucking Sylvain hard and fast. Sylvain had been reduced to a moaning mess against the walls, trying and failing to move back against him.

"_Ahhn_ … use me up, fuck me like you've been fucking your hands all along and wishing it was him." Dimitri's hand moved from Sylvain's hair to his mouth, shoving two fingers in and making him suck.

"Shut up."

Felix had seen this side of Dimitri various times: this cold, ruthless Dimitri. He had learned to love both sides of him: the side that would leave open mouth kisses along his thighs for thirty straight minutes, and the side that ripped his clothes off and made him bleed. Both sides had their merit, but watching him absolutely brutalize Sylvain's ass and choke on his fingers was doing something to his brain that he couldn't quite figure out. He spit into his palm and stroked himself faster, picturing himself against that wall, now more excited than ever to have Dimitri finally fuck him.

Meanwhile, Sylvain was covered in his own spit and moaning at each thrust, his cock leaking precome onto the carpet. Dimitri reached around and squeezed him at the base, burying himself deep. Sylvain squeezed around him tight, impossibly tight, and Dimitri came without warning, bucking a few times haphazardly as he rode out his orgasm. He pulled out and most of the spend fell right out of Sylvain, laughing as he turned back to face the two.

"You've got your work cut out for you, Felix! Shit, I haven't been fucked like that in ages." He wiped the sweat from his head with the back of his hand, grabbing the little booty shorts and pulling them back on over his still-hard cock.

"Do uh. Do demons not come?"

"Oh, they do, humans just don't really last long enough." He smirked, his face stained with drool and sweat, as if he hadn't just been fucked up against a wall and previously been balls deep in someone else. Despite all of that, he looked unphased and beautiful, completely untouched. The only giveaway of their encounter was the purple bruise on his hip, peeking out from the cherry-red shorts.

"This was a lot of fun though, normally girls summon me. Been a long time since I had guys call me up." Felix tried not to think about how calculated this all was on Annette's part. She had given him all the tools they had needed to summon a sex demon, of all things, to help them in bed. Which meant this was not new territory for her. He'd text her later.

"If we want to call you again, do we need the board?" Dimitri took Felix's hand and squeezed it reassuringly.

Sylvain's hands went up behind his head, winking at Dimitri. "Aww, you gonna miss me? Sure, I'll come by again for that big dick any time you need, baby. All you need is those candles, rose oil, and my name. I'll come back, if I'm not busy on another house call." Dimitri rolled his eyes and tried not to blush, pulling his pants back up.

"Good to know. You can take your leave now, we have … some cleaning up to do." Felix took the time to look around now and noticed just how much of a mess they had made: the carpet looked disgusting, the wall was covered in sweat and handprints, and they both desperately needed a shower.

"All right, love birds, enjoy your first time. If I may make a suggestion-"

"Leave." Felix bared his teeth and Sylvain laughed, disappearing in a cloud of smoke. Felix turned back to face Dimitri, his boyfriend, the man he loved, and tried to piece together exactly what just happened.

"... I'm going to talk to Annette about this." Was the only thing Felix could make himself say.

"Was that at least a little helpful?" Dimitri tilted Felix's face up and smiled at him, earning him a fraction of a smile in return.

"A little. Excited for when it's you."

"Me too." They kissed, holding each other close until they both decided they were too gross and needed to shower.

When Felix brought it up to Annette the next day, she just laughed and brushed him off, taking the board and snapped planchette back. She said nothing else on the matter, which Felix realized he was probably be grateful for. The last thing he needed to think about was Annette calling up that gross sex demon and having her way with him. Gross.

**Author's Note:**

> I am furious how easy this was to write this, do not look at me  
If you want to come talk to me about this on Twitter at @danivonfemblem if you want to see more of this absolute debauchery


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